1. Field
Embodiments of the invention relate to a primary side regulator.
2. Description of the Related Art
In power factor correction, an output voltage has a large ripple with respect to a frequency of a line input voltage. Since the line input voltage is a voltage in which an alternating current input is rectified, and a diode current is a function of the square of the line input voltage, the diode current is a sine squared function. An inductor current is rectified through a diode, and the rectified current is referred to as the diode current.
A primary side regulator for regulating an output current and an output voltage estimates a diode current and the output voltage. At this time, a large current ripple may be included in an output current estimation result since the square of the ripple of the line input voltage has an influence on the output current estimation. Further, the ripple of the line input voltage may also have an influence on the output voltage estimation, and thus the large voltage ripple may be included in the output voltage estimation result.
Therefore, there is a problem in that an output of an error amplifier has a large voltage ripple due to the ripple of the estimated output voltage, and a duty ratio is not constant even during one period of the line input voltage. This causes a low power factor. Further, constant current (CC) performance is decreased and a kick-in and kick-out phenomenon occurs due to the ripple of the estimated output current.